MESOSCALE DISCUSSION 0626 NWS STORM PREDICTION CENTER NORMAN OK 0105 PM CDT WED APR 27 2011 AREAS AFFECTED...MUCH OF AL INTO MIDDLE TN/NORTHWEST GA CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY VALID 271805Z - 271930Z A LONG DURATION PARTICULARLY DANGEROUS /PDS/ TORNADO WATCH WILL BE ISSUED BY MID AFTERNOON FOR MUCH OF AL INTO MIDDLE TN/NORTHWEST GA...WITH AN ISSUANCE PROBABLE BY AROUND 19Z. AMID CLOUD BREAKS...THE AIRMASS CONTINUES TO QUICKLY DESTABILIZE IN THE WAKE OF A DECAYING MORNING WEST-EAST BOUNDARY ACROSS AL...AND TO THE SOUTH OF A MORE RECENT MCS-INDUCED BOUNDARY/COLD POOL ACROSS FAR NORTHERN AL. WITH A CLASSIC/SYNOPTICALLY EVIDENT OUTBREAK SETUP VIA A SHORTWAVE TROUGH/STRONG JET STREAK CURRENTLY NEARING THE LOWER-MIDDLE MS RIVER VALLEY PER SATELLITE IMAGERY...AN INCREASINGLY VOLATILE SETUP IS LIKELY THROUGH THE AFTERNOON. SUPERCELLS CAPABLE OF STRONG/VIOLENT TORNADOES ARE EXPECTED TO BECOME PREVALENT ACROSS AN INCREASINGLY UNSTABLE/WEAKLY CAPPED WARM SECTOR...WITH WSR-88D VWP OBSERVED AND RUC FORECASTS REFLECTING INCREASINGLY LONG/LOOPING LOW LEVEL HODOGRAPHS. IN THE WAKE OF A MORNING SEVERE MCS...THE AIRMASS IS EXPECTED TO RAPIDLY RECOVER ACROSS FAR NORTHERN AL INTO MIDDLE TN BY LATE AFTERNOON/EARLY EVENING. ..GUYER.. 04/27/2011